Paris, France — French officials solved an awkward seating dilemma at the Notre Dame cathedral re-opening on Saturday by placing First Lady Brigitte Macron between US President-elect Donald Trump and Joe Biden's wife and daughter in the front row at the ceremony.

The presence of Trump and the outgoing president's family presented protocol planners with a headache so soon after one of the most bitter election campaigns in US history.

Trump ridiculed Biden as "Sleepy Joe" throughout, while Biden called Trump a "threat to democracy" and let it be known that he considered him a "fascist" on the eve of the November 5 vote. 

The future 47th president was treated as guest of honour on Saturday in Paris, given the seat immediately to French President Emmanuel Macron's right in the front row of the congregation. 

Jill Biden, representing the outgoing president, as well as the couple's daughter Ashley, were also seated on the front row but with Brigitte separating them from Trump.

President Biden, 82, decided against travelling to Paris and appeared visibly tired as he made a historic first visit by a US leader to Angola in southern Africa on Tuesday and Wednesday.   

Before the start of the ceremony, the US first lady and Trump found themselves seated on their own briefly and could be seen exchanging pleasantries. 

Trump made his trademark raised fist gesture -- immortalised when he survived an assassination attempt in July -- as he entered the cathedral.

Wearing an uncharacteristic yellow tie, he stopped briefly to talk to Prince William, heir to the British throne, before taking his seat.